# ---
# title: 1497. Check If Array Pairs Are Divisible by k
# id: problem1497
# author: Tian Jun
# date: 2020-10-31
# difficulty: Medium
# categories: Array, Math, Greedy
# link: <https://leetcode.com/problems/check-if-array-pairs-are-divisible-by-k/description/>
# hidden: true
# ---
# 
# Given an array of integers `arr` of even length `n` and an integer `k`.
# 
# We want to divide the array into exactly `n / 2` pairs such that the sum of
# each pair is divisible by `k`.
# 
# Return _True_ If you can find a way to do that or _False_ otherwise.
# 
# 
# 
# **Example 1:**
# 
#     
#     
#     Input: arr = [1,2,3,4,5,10,6,7,8,9], k = 5
#     Output: true
#     Explanation: Pairs are (1,9),(2,8),(3,7),(4,6) and (5,10).
#     
# 
# **Example 2:**
# 
#     
#     
#     Input: arr = [1,2,3,4,5,6], k = 7
#     Output: true
#     Explanation: Pairs are (1,6),(2,5) and(3,4).
#     
# 
# **Example 3:**
# 
#     
#     
#     Input: arr = [1,2,3,4,5,6], k = 10
#     Output: false
#     Explanation: You can try all possible pairs to see that there is no way to divide arr into 3 pairs each with sum divisible by 10.
#     
# 
# **Example 4:**
# 
#     
#     
#     Input: arr = [-10,10], k = 2
#     Output: true
#     
# 
# **Example 5:**
# 
#     
#     
#     Input: arr = [-1,1,-2,2,-3,3,-4,4], k = 3
#     Output: true
#     
# 
# 
# 
# **Constraints:**
# 
#   * `arr.length == n`
#   * `1 <= n <= 10^5`
#   * `n` is even.
#   * `-10^9 <= arr[i] <= 10^9`
#   * `1 <= k <= 10^5`
# 
# 
## @lc code=start
using LeetCode

## add your code here:
## @lc code=end
